Recently, an ultrasound system has been extensively used in the medical field due to its non-invasive and non-destructive nature. Modern high-performance ultrasound imaging diagnostic systems and techniques are typically used to produce two- or three-dimensional ultrasound images of internal features of patients. To provide the ultrasound images, the ultrasound system operates in various image modes such as a brightness mode, a Doppler mode and the like to acquire ultrasound images for diagnosis.
In the Doppler mode, the ultrasound system provides a color Doppler mode image visualizing velocities of moving objects such as blood flow, heart, etc. The color Doppler mode image includes a power image visualizing powers of Doppler signals as 2-dimensional distribution and a velocity image visualizing velocities of the moving objects, which may be computed from the Doppler signals, as 2-dimensional distribution. The color Doppler mode image may visualize the blood flow in real time in a wide range from the blood flow of a high velocity in a large vessel to the blood flow of a low velocity in a small vessel.
Conventionally, smoothing has been carried out upon the velocity image for enhancement. However, since the blood flow on the velocity image may be extended to the vessel region due to the smoothing, bleeding, which shows blood escape from the real vessel on the velocity image, may be caused. Further, a loss of small vessels may occur. Also, the connectivity loss, i.e., portions of vessel are cut in the velocity image, may be generated. The peaks of the blood flow may be important clinical information in the velocity image. However, the peak loss, i.e., peaks of the blood flow are disappeared in the velocity image, may be also generated due to the smoothing thereupon.
Further, the effectiveness of pixels in the power image is determined through the fixed thresholding method. However, since the power of blood flow varies according to the heartbeat, the vascular collapse, i.e., the blood vessel region is collapsed in the power image, may occur.